The Syrian government and the rebels have each accused the other of using chemical weapons in a missile attack that killed 25 people on Tuesday, though U.S. and British officials have expressed skepticism that such weapons were used at all. President Obama has described chemical weapons being used or moved in large numbers as a "red line" for the U.S. government's decision to intervene in the ongoing civil war.

According to the regime, more than 80 people were injured in the attack on Khan al-Asal, a town in the Aleppo province; the Syrian Observatory for Human Rights has confirmed that 16 soldiers in the Syrian army were killed. Russia, one of Syria's remaining international backers, claimed to have "information" showing the rebels had used chemical weapons, but the rebels denied the charge categorically:

"The area that was targeted is under rebels' control, so it is quite absurd that the regime would accuse us of attacking our own people," [Free Syrian Army spokesman Louay Almokdad] said.

"The Assad regime possesses chemical agents and they already used weapons of mass destruction against its own people, so we do expect the worse from this brutal psychopathic regime," he said. "The international community must take these attacks against our civilian population seriously. It is time to put an end to the daily mass killings in Syria."

White House Press Secretary Jay Carney told reporters that the Obama administration had no evidence that rebels had used the weapons, and was looking into the charges. State Department officials interviewed by CNN said they doubted rebels could obtain chemical weapons, but also thought it unlikely that the regime had used them, either. Britain's envoy to the U.N. said reports had not been verified, and the independent Organization for the Prohibition of Chemical Weapons could not confirm that they had been used.